As his helicopter slalomed through a dozen sky-high columns of smoke from fires set by poachers clearing Macarena National Park, Brando saw endless "craters" of lime-green coca. He likened the park's once unbroken carpet of dark green primeval forest, now scarred by roads, fires and illegal chemicals, to "the black-and-white palette of war."

Brando, the author of a dozen photography books, had retained only positive images of his last flight over the park 12 years ago. He had been awestruck by the park's geologic formations related to Venezuela's tepui mesas, which resemble giant black souffles. He was dazzled by the crystal canyon where underwater plant life gives its arterial river a bright vermilion hue.

Now he felt stunned by the "terrible kind of impressionism" and bleak panorama of the coca farmers' destruction.

Leftist rebels, right-wing paramilitaries and narcos that control the billion-dollar cocaine trade have invaded the 2.5-million-acre Macarena, laying waste to much of it to plant coca. Most of Colombia's 48 other national parks and nature reserves are suffering similar fates. Chased from more accessible sites by U.S.-sponsored aerial fumigation, coca growers relentlessly clear forests knowing that they are beyond the reach of the U.S.-Colombian fleet of planes because spraying of the parks is prohibited by law.

Counternarcotics officials estimate that narcos have carved out as many as 4,000 coca sites in the Macarena, each averaging no more than 4 acres.

The result has been incalculable environmental damage. The helicopter overflight, offered to Brando as part of a government program to publicize the damage being caused by cocaine traffickers, provided a rarely seen perspective of out-of-control devastation.

Naturalists are especially concerned about the damage being done in the Macarena because of its unique confluence of Andean, Amazonian and Orinocan ecology. Forest on the eastern side of the park has been decimated, and rivers have been fouled by toxic chemicals used by narcos to clear overgrowth and process cocaine.

Luis Alfonso Ortega, a biologist with Fundacion Ecohabitats in Popayan, said that Colombia is losing tens of thousands of acres a year to deforestation and that the rate is five times faster in its national parks.

"This makes me very sad because the Macarena is the Colombian reserve most valued by conservationists," Ortega said. "There are 450 species of birds, eight of monkeys and no one knows how many plants. There has been no full-scale investigation because of security concerns."

In a recent interview, Colombian Vice President Francisco Santos admitted that his nation's options in stopping coca farmers are limited, given the parks' remoteness, the ban on spraying and the limited numbers of crews available to manually eradicate coca.

To make matters worse, Colombian and U.S. counternarcotics officials who wish to remove coca plants find it an often hazardous endeavor because of land mines, snipers and other perils. Chemicals used by coca farmers to clear land and process cocaine also pose health hazards.

Since 2000, about 90 workers have been killed uprooting coca plants. In August 2006, six workers clearing coca in the Macarena were killed by a remote-controlled bomb apparently set by the Revolutionary Armed Forces of Colombia, the rebel militia known as the FARC, whose zone of influence has long included the national park.

After that attack, Colombian President Alvaro Uribe persuaded Congress to waive the prohibition on aerial eradication in national parks to spray coca plants in the Macarena for several months. This year, the government, with financial and material assistance from the United States, is targeting 250,000 acres for manual eradication, up 33 percent from last year. One hundred teams, each with 30 workers and 120 armed guards, this month began fanning out across remote sites including Macarena to uproot the illicit crops.

Meanwhile, total acreage selected for aerial spraying of herbicide under the auspices of Plan Colombia, the U.S.-financed anti-drug and -terrorism aid package, will decline 15 percent in 2008 to about 320,000 acres.

After his aerial tour, Brando was briefed on eradication plans for 2008 by Colombian anti-drug police at a military base east of the 2.5-million-acre park. He acknowledged later that his mind remained on the stark images he saw of the creeping destruction of his country, which is one of the world's most biodiverse.

"The craters," the photographer said, shaking his head, "were like a flesh-eating disease over the skin of the Earth."